U.S. Pat. Nos. 3,979,399, 3,840,546, and 3,966,746 (E.R. Squibb & Sons) disclose 4-amino derivatives of pyrazolo[3,4-b]pyridine-5-carboxamides wherein the 4-amino group NR3R4 can be an acyclic amino group wherein R3 and R4 may each be hydrogen, lower alkyl (e.g. butyl), phenyl, etc.; NR3R4 can alternatively be a 3-6-membered heterocyclic group such as pyrrolidino, piperidino and piperazino. The compounds are disclosed as central nervous system depressants useful as ataractic, analgesic and hypotensive agents.
U.S. Pat. Nos. 3,925,388, 3,856,799, 3,833,594 and 3,755,340 (E.R. Squibb & Sons) disclose 4-amino derivatives of pyrazolo[3,4-b]pyridine-5-carboxylic acids and esters. The 4-amino group NR3R4 can be an acyclic amino group wherein R3 and R4 may each be hydrogen, lower alkyl (e.g. butyl), phenyl, etc.; NR3R4 can alternatively be a 5-6-membered heterocyclic group in which an additional nitrogen is present such as pyrrolidino, piperidino, pyrazolyl, pyrimidinyl, pyridazinyl or piperazinyl. The compounds are mentioned as being central nervous system depressants useful as ataractic agents or tranquilisers, as having antiinflammatory and analgesic properties. The compounds are mentioned as increasing the intracellular concentration of adenosine-3′,5′-cyclic monophosphate and for alleviating the symptoms of asthma.
H. Hoehn et al., J. Heterocycl. Chem., 1972, 9(2), 235-253 discloses a series of 1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid derivatives with 4-hydroxy, 4-chloro, 4-alkoxy, 4-hydrazino, and 4-amino substituents. Ethyl 4-(n-butylamino)-1-ethyl-1H-pyrazolo[3,4-b]-pyridine-5-carboxylate is disclosed therein; this compound is cartazolate.
The compound tracazolate, ethyl 4-(n-butylamino)-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]-pyridine-5-carboxylate, is known as an anxiolytic agent (e.g. see J. B. Patel et al., Eur. J. Pharmacol., 1982, 78, 323). Other 1-substituted 4-(NH2 or NH-alkyl)-1H-pyrazolo[3,4-b]-pyridine-5-carboxylic acid esters and amides are disclosed as potential anxiolytic agents in T. M. Bare et al., J. Med. Chem., 1989, 32, 2561-2573.
CA 1003419, CH 553 799 and T. Denzel, Archiv der Pharmazie, 1974, 307(3), 177-186 disclose 4,5-disubstituted 1H-pyrazolo[3,4-b]pyridines unsubstituted at the 1-position.
Japanese laid-open patent application JP-2002-20386-A (Ono Yakuhin Kogyo KK) published on 23 Jan. 2002 discloses pyrazolopyridine compounds of the following formula:
wherein R1 denotes 1) a group —OR6, 2) a group —SR7, 3) a C2-8 alkynyl group, 4) a nitro group, 5) a cyano group, 6) a C1-8 alkyl group substituted by a hydroxy group or a C1-8 alkoxy group, 7) a phenyl group, 8) a group —C(O)R8, 9) a group —SO2NR9R10, 10) a group —NR11SO2R12, 11) a group —NR13C(O)R14 or 12) a group —CH═NR15. R6 and R7 denote i) a hydrogen atom, ii) a C1-8 alkyl group, iii) a C1-8 alkyl group substituted by a C1-8 alkoxy group, iv) a trihalomethyl group, v) a C3-7 cycloalkyl group, vi) a C1-8 alkyl group substituted by a phenyl group or vii) a 3-15 membered mono-, di- or tricyclic hetero ring containing 1-4 nitrogen atoms, 1-3 oxygen atoms and/or 1-3 sulphur atoms. R2 denotes 1) a hydrogen atom or 2) a C1-8 alkoxy group. R3 denotes 1) a hydrogen atom or 2) a C1-8 alkyl group. R4 denotes 1) a hydrogen atom, 2) a C1-8 alkyl group, 3) a C3-7 cycloalkyl group, 4) a C1-8 alkyl group substituted by a C3-7 cycloalkyl group, 5) a phenyl group which may be substituted by 1-3 halogen atoms or 6) a 3-15 membered mono-, di- or tricyclic hetero ring containing 1-4 nitrogen atoms, 1-3 oxygen atoms and/or 1-3 sulphur atoms. R5 denotes 1) a hydrogen atom, 2) a C1-8 alkyl group, 3) a C3-7 cycloalkyl group, 4) a C1-8 alkyl group substituted by a C3-7 cycloalkyl group or 5) a phenyl group which may be substituted by 1-3 substituents. In group R3, a hydrogen atom is preferred. In group R4, methyl, ethyl, cyclopropyl, cyclobutyl or cyclopentyl are preferred. The compounds of JP-2002-20386-A are stated as having PDE4 inhibitory activity and as being useful in the prevention and/or treatment of inflammatory diseases and many other diseases.
1,3-Dimethyl-4-(arylamino)-pyrazolo[3,4-b]pyridines with a 5-C(O)NH2 substituent similar or identical to those in JP-2002-20386-A were disclosed as orally active PDE4 inhibitors by authors from Ono Pharmaceutical Co. in: H. Ochiai et al., Bioorg. Med. Chem. Lett., 5th Jan. 2004 issue, vol. 14(1), pp. 29-32 (available on or before 4th Dec. 2003 from the Web version of the journal: “articles in press”). Full papers on these and similar compounds as orally active PDE4 inhibitors are: H. Ochiai et al., Bioorg. Med. Chem., 2004, 12(15), 4089-4100 (stated to have been available online 20 Jun. 2004), and H. Ochiai et al., Chem. Pharm. Bull., 2004, 52(9), 1098-1104 (stated to have been published online 15 Jun. 2004).
EP 0 076 035 A1 (ICI Americas) discloses pyrazolo[3,4-b]pyridine derivatives as central nervous system depressants useful as tranquilisers or ataractic agents for the relief of anxiety and tension states.
J. W. Daly et al., Med. Chem. Res., 1994, 4, 293-306 and D. Shi et al., Drug Development Research, 1997, 42, 41-56 disclose a series of 4-(amino) substituted 1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid derivatives, including ethyl 4-cyclopentylamino-1-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate, and their affinities and antagonist activities at A1- and A2A-adenosine receptors, and the latter paper discloses their affinities at various binding sites of the GABAA-receptor channel. S. Schenone et al., Bioorg. Med. Chem. Lett., 2001, 11, 2529-2531, and F. Bondavalli et al., J. Med. Chem., 2002, vol. 45 (Issue 22, 24 Oct. 2002, allegedly published on Web Sep. 24, 2002), pp. 4875-4887 disclose a series of 4-amino-1-(2-chloro-2-phenylethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl esters as A1-adenosine receptor ligands.
WO 02/060900 A2 appears to disclose, as MCP-1 antagonists for treatment of allergic, inflammatory or autoimmune disorders or diseases, a series of bicyclic heterocyclic compounds with a —C(O)—NR4—C(O)—NR5R6 substituent, including isoxazolo[5,4-b]pyridines and 1H-pyrazolo[3,4-b]pyridines (named as pyrazolo[5,4-b]pyridines) with the —C(O)—NR4—C(O)—NR5R6 group as the 5-substituent and optionally substituted at the 1-, 3-, 4-, and/or 6-positions. Bicyclic heterocyclic compounds with a —C(O)NH2 substituent instead of the —C(O)—NR4—C(O)—NR5R6 substituent are alleged to be disclosed in WO 02/060900 as intermediates in the synthesis of the —C(O)—NR4—C(O)—NR5R6 substituted compounds. See also WO 02/081463 A1 for similar MCP-1 antagonists.
WO 00/15222 (Bristol-Myers Squibb) discloses inter alia pyrazolo[3,4-b]pyridines having inter alia a C(O)—X1 group at the 5-position and a group E1 at the 4-position of the ring system. Amongst other things, X1 can for example be —OR9, —N(R9)(R10) or —N(R5)(-A2-R2), and E1 can for example be —NH-A1-cycloalkyl, —NH-A1-substituted cycloalkyl, or —NH-A1-heterocyclo; wherein A1 is an alkylene or substituted alkylene bridge of 1 to 10 carbons and A2 can for example be a direct bond or an alkylene or substituted alkylene bridge of 1 to 10 carbons. The compounds are disclosed as being useful as inhibitors of cGMP phosphodiesterase, especially PDE type V, and in the treatment of various cGMP-associated conditions such as erectile dysfunction. Compounds with a cycloalkyl or heterocyclo group directly attached to —NH— at the 4-position of the pyrazolo[3,4-b]pyridine ring system and/or having PDE4 inhibitory activity do not appear to be disclosed in WO 00/15222.
G. Yu et. al., J. Med. Chem., 2001, 44, 1025-1027 discloses some 4-[(3-chloro-4-methoxybenzyl)amino]-pyrazolopyridine-5-carboxamides as selective PDE5 inhibitors.
H. de Mello, A. Echevarria, et al., J. Med. Chem., 2004, 47 (22), 5427-5432, believed to have been published online on or before 21 Sep. 2004, discloses 3-methyl or 3-phenyl 4-anilino-1H-pyrazolo[3,4-b]pyridine 5-carboxylic esters as potential anti-Leishmania drugs.
Copending patent application PCT/EP2003/014867, filed on 19 Dec. 2003 in the name of Glaxo Group Limited, published on 8 Jul. 2004 as WO 2004/056823 A1, discloses and claims pyrazolo[3,4-b]pyridine compounds or salts thereof with a 4-NR3R3a group (R3a is preferably H) and with a group Het at the 5-position of the pyrazolo[3,4-b]pyridine, wherein Het is usually a 5-membered optionally substituted heteroaryl group. PCT/EP2003/014867 (WO 2004/056823 A1) also discloses the use of these compounds as PDE4 inhibitors and for the treatment and/or prophylaxis of inter alia COPD, asthma or allergic rhinitis.
Copending patent application PCT/EP03/11814, filed on 12 Sep. 2003 in the name of Glaxo Group Limited, published on 25 Mar. 2004 as WO 2004/024728 A2, discloses pyrazolo[3,4-b]pyridine compounds or salts thereof with a 4-NHR3 group and a 5-C(O)—X group, according to this formula (I):
wherein:
R1 is C1-4alkyl, C1-3fluoroalkyl, —CH2CH2OH or —CH2CH2CO2C1-2alkyl;
R2 is a hydrogen atom (H), methyl or C1fluoroalkyl;
R3 is optionally substituted C3-8cycloalkyl or optionally substituted mono-unsaturated-C5-7cycloalkenyl or an optionally substituted heterocyclic group of sub-formula (aa), (bb) or (cc);
in which n1 and n2 independently are 1 or 2; and in which Y is O, S, SO2, or NR10; where R10 is a hydrogen atom (H), C1-4alkyl, C1-2fluoroalkyl, CH2C(O)NH2, C(O)NH2, C(O)—C1-2alkyl, C(O)—C1fluoroalkyl or —C(O)—CH2O—C1-2alkyl; or R3 is a bicyclic group (dd) or (ee):
and wherein X is NR4R5 or OR5a.
In PCT/EP03/11814 (WO 2004/024728 A2), R4 is a hydrogen atom (H); C1-6alkyl; C1-3fluoroalkyl; or C2-6alkyl substituted by one substituent R11.
In PCT/EP03/11814 (WO 2004/024728 A2), R5 can be: a hydrogen atom (H); C1-8alkyl; C1-8 fluoroalkyl; C3-8cycloalkyl optionally substituted by a C1-2alkyl group; —(CH2)n4—C3-8cycloalkyl optionally substituted, in the —(CH2)n4— moiety or in the C3-8cycloalkyl moiety, by a C1-2alkyl group, wherein n4 is 1, 2 or 3; C2-6alkyl substituted by one or two independent substituents R11; —(CH2)n11—C(O)R16; —(CH2)n12—C(O)NR12R13; —CHR19—C(O)NR12R13; —(CH2)n12—C(O)OR16; —(CH2)n12—C(O)OH; —CHR19—C(O)OR16; —CHR19—C(O)OH; —(CH2)n12—SO2—NR12R13; —(CH2)n12—SO2R16; or —(CH2)n12—CN; —(CH2)n13-Het; or optionally substituted phenyl.
Alternatively, in PCT/EP03/11814 (WO 2004/024728 A2), R5 can have the sub-formula (x), (y), (y1) or (z):
wherein in sub-formula (x), n=0, 1 or 2; in sub-formula (y) and (y1), m=1 or 2; and in sub-formula (z), r=0, 1 or 2; and wherein in sub-formula (x) and (y) and (y1), none, one or two of A, B, D, E and F are independently nitrogen or nitrogen-oxide (N+—O−) provided that no more than one of A, B, D, E and F is nitrogen-oxide, and the remaining of A, B, D, E and F are independently CH or CR6; and provided that when n is 0 in sub-formula (x) then one or two of A, B, D, E and F are independently nitrogen or nitrogen-oxide (N+—O−) and no more than one of A, B, D, E and F is nitrogen-oxide;
In PCT/EP03/11814 (WO 2004/024728 A2), each R6, independently of any other R6 present, is: a halogen atom; C1-6alkyl; C1-4fluoroalkyl; C1-4alkoxy; C1-2fluoroalkoxy; C3-6cycloalkyloxy; —C(O)R16a; —C(O)OR30; —S(O)2—R16a; R16a—S(O)2—NR15a—; R7R8N—S(O)2—; C1-2alkyl-C(O)—R15aN—S(O)2—; C1-4alkyl-S(O)—; Ph-S(O)—; R7R8N—CO—; —NR15—C(O)R16; R7R8N; OH; C1-4alkoxymethyl; C1-4alkoxyethyl; C1-2alkyl-S(O)2—CH2—; R7R8N—S(O)2—CH2—; C1-2alkyl-S(O)2—NR15a—CH2—; —CH2—OH; —CH2CH2—OH; —CH2—NR7R8; —CH2—CH2—NR7R8; —CH2—C(O)OR30; —CH2—C(O)—NR7R8; —CH2—NR15a—C(O)—C1-3alkyl; —(CH2)n14-Het1 where n14 is 0 or 1; cyano (CN); Ar5b; or phenyl, pyridinyl or pyrimidinyl wherein the phenyl, pyridinyl or pyrimidinyl independently are optionally substitutes by one or two of fluoro, chloro, C1-2alkyl, C1fluoroalkyl, C1-2alkoxy or C1fluoroalkoxy; or two adjacent R6 taken together can be —O—(CMe2)-O— or —O—(CH2)n14—O— where n14 is 1 or 2.
The pyrazolo[3,4-b]pyridine compounds of formula (I) and salts thereof disclosed in PCT/EP03/11814 (WO 2004/024728 A2) are disclosed as being inhibitors of phosphodiesterase type IV (PDE4), and as being useful for the treatment and/or prophylaxis of a variety of diseases/conditions, especially inflammatory and/or allergic diseases, in mammals such as humans, for example: asthma, chronic obstructive pulmonary disease (COPD) (e.g. chronic bronchitis and/or emphysema), atopic dermatitis, urticaria, allergic rhinitis, allergic conjunctivitis, vernal conjunctivitis, eosinophilic granuloma, psoriasis, rheumatoid arthritis, septic shock, ulcerative colitis, Crohn's disease, reperfusion injury of the myocardium and brain, chronic glomerulonephritis, endotoxic shock, adult respiratory distress syndrome, multiple sclerosis, cognitive impairment (e.g. in a neurological disorder), depression, or pain. PCT/EP03/11814 (WO 2004/024728 A2) states that the compounds of formula (I) and/or their pharmaceutical compositions may be administered by oral, parenteral, inhaled (topical to the lung), or nasal administration. However, the use of the pyrazolo[3,4-b]pyridine compounds by external topical administration is not disclosed.
Also, PCT/EP03/11814 (WO 2004/024728 A2) does not disclose any specific pyrazolo[3,4-b]pyridine compounds having a 4-position group NHR3 in which R3 is an optionally substituted heterocyclic group of sub-formula (aa), (bb) or (cc) and in which Y is NR10 wherein R10 is C(O)NH2.
WO 2004/024728 has been reviewed, and WO 2004/056823 mentioned, in Expert Opin. Ther. Patents, 2005 (January edition), 15(1), 111-114.